For the production of food material, mankind has long since used various microorganisms, such as yeast, fungi or bacteria, so as to modify, prepare or change the nature or taste of foodstuffs. One such kind of microorganisms are the soil bacteria belonging to the Bacillus subtilis group that are used for the fermentation of different plants tissues, such as beans, e.g., soybeans and (African) locust beans, and seeds, e.g., the seeds of African oil bean, cotton seeds, melon seeds, etc. In the fermentation process, B. subtilis degrades cellulose and/or the protein material contained in the starting material resulting in a fermented product that may be further processed or is already ready for consumption.
One bacteria very closely related to B. subtilis is the so-called strain B. natto, a food-grade, gram-positive microorganism mainly used for the fermentation of soybeans, which fermentation process eventually results in a cheap and nutritious food that is rich in amino acids. The term B. natto is derived from the Japanese soybean fermented product “Natto” that is commercially produced and often eaten at breakfast (see also K. H. Steinkraus et al., Handbook of Indigenous Fermented Food, Vol. 9, (1983), 530-547).
A drawback in the fermentation of biological starting materials with microorganisms for food production resides in that a variety of by-products are generated that are not desirable by the consumer, such as an off-flavor or an unwanted hardness of the product. To this end, Japanese application no. 08-275772 describes the use of a particular strain of B. subtilis for reducing the amount of ammonia in the end product “Natto”. This objective is achieved by keeping the protease activity during the early stage of fermentation at a high level, so that essentially all soybean proteins are degraded to a substantial degree, while in a later stage of fermentation the protease activity is remarkably reduced so as not to produce extensive amounts of ammonia which would eventually deteriorate the smell of the food product.
In Japanese application no. 09-009903, there is a described another B. subtilis strain that has improved hemicellulose degrading properties such that the end product reveals an increased softness.
Although the properties of food products derived from a fermentation with microorganisms such as B. subtilis have been improved in various respects, there is still a need for a further improvement of the taste and/or smell of the final end product. The present invention now satisfies that need.